1. Field of the Invention
The invention relates generally to the field of microelectronic fabrication. More particularly, the invention relates to the fabrication of polymeric microelectronic structures, such as photoresist masks and low dielectric constant materials.
2. Discussion of the Related Art
The manufacturing of advanced semiconductors requires the production of circuit features at the sub micron level. A very sensitive photoresist is needed to define these features. The problems encountered in obtaining the maximum performance out of these sensitive photoresists is known to those skilled in the art of photolithography.
A class of new generation deep ultra-violet (DUV) chemically amplified photoresists based on "ACETAL" chemistry is required to produce features between 0.10-0.25 um using an exposure wavelength of 248 nm. One problem with ACETAL-based photoresists is that they are very sensitive to the chemical environment throughout the lithography process sequence. This is due to the fact that the chemical "deprotection" reaction that takes place during the post exposure bake (PEB) process requires the presence of moisture along with a photacid created during the previous exposure step. If the previous post application bake (PAB) process conditions and the stepper environment are not carefully optimized, and film moisture content decreases below a certain value, the ultimate lithographic performance of these photoresists will deteriorate significantly. Since deprotection has to occur at a precise time in the process sequence the moisture content at any given time of the process sequence is critical. What is needed is a solution to this moisture sensitivity.
The second problem with the ACETAL-based chemistries is that deblocking reaction rate of an ACETAL-based resist is much faster than the less sensitive DUV chemistries such as T--BOC resists due to a weak H--O physical bond. This is why the deblocking reaction starts at room temperature, thus causing contamination of the projection optics of the exposure tools (step and scanner) during the exposure step. What is also needed is a solution to this temperature sensitivity.
Heretofore, the requirements of obviating moisture and temperature sensitivity referred to above have not been fully met. What is needed is a solution that simultaneously addresses all of these requirements.